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feat(lab03): use epoll and timer for led

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This commit is contained in:
Rémi Heredero
2026-04-24 13:20:46 +00:00
parent 8561386973
commit 2d26f30adf
1 changed files with 28 additions and 24 deletions
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52
src/03-led-controller/main.c
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@@ -43,6 +43,7 @@
#define GPIO_LED "/sys/class/gpio/gpio10" #define GPIO_LED "/sys/class/gpio/gpio10"
#define LED "10" #define LED "10"
#define DEFAULT_TIME_MS 1000 #define DEFAULT_TIME_MS 1000
#define DUTY_CYCLE_PERCENT 2
typedef struct { typedef struct {
int timer_fd; int timer_fd;
@@ -72,7 +73,7 @@ static int open_led() {
static void toggle_led(int led) { static void toggle_led(int led) {
static int k = 0; static int k = 0;
if (k%2 == 1) { if (k%2 == 0) {
printf("ping %d\n", k>>1); printf("ping %d\n", k>>1);
pwrite(led, "1", sizeof("1"), 0); pwrite(led, "1", sizeof("1"), 0);
} else { } else {
@@ -87,28 +88,35 @@ static void* timer_thread(void* arg) {
int led = open_led(); int led = open_led();
pwrite(led, "1", sizeof("1"), 0); pwrite(led, "1", sizeof("1"), 0);
long period = DEFAULT_TIME_MS * 1000000; // ns
long flash_period_ms = DEFAULT_TIME_MS / 100 * DUTY_CYCLE_PERCENT; // 2% duty
// compute duty period... struct epoll_event ev;
long p1 = period / 100 * 2; // 2% duty cycle
long p2 = period - p1;
struct timespec t1;
clock_gettime(CLOCK_MONOTONIC, &t1);
int k = 0;
while(1) { while(1) {
struct timespec t2;
clock_gettime(CLOCK_MONOTONIC, &t2);
long delta = (t2.tv_sec - t1.tv_sec) * period + (t2.tv_nsec - t1.tv_nsec); int n = epoll_wait(data->epoll_fd, &ev, 1, -1);
if (n == -1) {
int toggle = ((k == 0) && (delta >= p1)) | ((k == 1) && (delta >= p2)); perror("epoll_wait failed");
if (toggle) { break;
t1 = t2;
k = (k + 1) % 2;
toggle_led(led);
} }
uint64_t val;
if (read(data->timer_fd, &val, sizeof(val)) != sizeof(val)) {
perror("read timerfd failed");
break;
}
toggle_led(led);
struct timespec t1, t2;
clock_gettime(CLOCK_MONOTONIC, &t1);
t2.tv_sec = t1.tv_sec + flash_period_ms / 1000;
t2.tv_nsec = t1.tv_nsec + (flash_period_ms % 1000) * 1000000;
while(t1.tv_sec < t2.tv_sec || (t1.tv_sec == t2.tv_sec && t1.tv_nsec < t2.tv_nsec)) {
clock_gettime(CLOCK_MONOTONIC, &t1);
}
toggle_led(led);
} }
return NULL; return NULL;
} }
@@ -165,10 +173,6 @@ int main(int argc, char* argv[]) {
link_timer_to_epoll(&data.timer_fd, &data.epoll_fd); link_timer_to_epoll(&data.timer_fd, &data.epoll_fd);
if (pthread_create(&thread, NULL, timer_thread, &data) != 0) { if (pthread_create(&thread, NULL, timer_thread, &data) != 0) {
perror("Failed to create timer thread"); perror("Failed to create timer thread");
exit(1); exit(1);